This invention relates to a method for promoting accumulation of fatty acids into the small intestinal epithelium, and also to a method for improving lipid metabolism in the small intestine epithelium for the suppression of triacylglycerol synthesis, the enhancement of β-oxidation, the enhancement of uncoupling protein (UCP) expression, the promotion of energy consumption, the lowering of blood leptin level, the lowering of blood remnant level and/or the like purpose. This invention is also concerned with a method for treating diabetes and a method for improving lipid metabolism in a diabetic patient by ingesting diacylglycerol.